The present invention relates generally to an image display system for displaying image information from measuring equipment, such as an echo sounder, and more particularly, the invention is concerned with a display system which can display more than one kind of image information received from a plurality of measuring devices in an integrated manner.
Today's modern fishing vessels and pleasure craft are equipped with a radar 1, a course plotter 2 incorporating, or connected to, a Global Positioning System (GPS) receiver, an echo sounder 3, and so on, as shown in FIG. 1. In a conventional onboard system of this kind, a dedicated indicator M1 is connected to the radar 1 by three signal lines for red (R), green (G) and blue (B) signals, signal lines for horizontal (H) and vertical (V) synchronizing signals. Similarly, an indicator M2 is connected to the course plotter 2 by its R, G and B signal lines and two synchronizing signal lines, while an indicator M3 is connected to the echo sounder 3 by its R, G and B signal lines and two synchronizing signal lines.
Since the aforementioned indicators M1–M3 are usually provided in a ship's bridge, the same number of additional indicators and signal lines become necessary if it is desired to monitor the same pictures as shown on the indicators M1–M3 in a remote location, such as a cabin, for example. The conventional onboard system has therefore been associated with the following problems:                A number of expensive indicators are required.        It is difficult to provide space for installing such multiple indicators.        Since three different pictures are individually shown on separate display screens, it is difficult for a viewer to give his or her consistent attention to the individual pictures, and this would result in a likelihood that the viewer could overlook important information.        